An end cover assembly of a conventional secondary battery is as shown in FIG. 1, in which a terminal substrate 100, a battery end cover 102, a pad 104 disposed between the terminal substrate 100 and the battery end cover 102 and a screw cap 106 are illustrated. Moreover, a pad 108 having an airtight or insulating function is disposed between the screw cap 106 and the battery end cover 102 for isolation. The end cover assembly of battery of FIG. 1 is suitable for welding to a tank of the secondary battery. However, in the above structure, when an external power line is locked to the terminal substrate 100, excessive force may cause air leakage between a base 110 of the terminal substrate 100 and the battery end cover 102 due to rotation, and electrolyte leakage may severely influence the battery performance and safety.
Therefore, there are a plenty of patents for ameliorating the end cover assembly of the secondary battery, for example, Taiwan Patent Publication No. 555164, in which a structure of a bottom surface of the battery end cover 102 is ameliorated to form a groove corresponding to a shape of the base 110 of the terminal substrate 100, so that shape matching of the base 110 and the groove may prevent the battery end cover 102 from unscrewing.
However, such structure amelioration still has a plenty of problems. For example, the screw cap 106 is liable to be loosed due to an external force (for example, vibration) to cause electrolyte leakage during a utilization period of the secondary battery.